Control method and apparatus



pr 4- J. J. SHIVELY ETAL CONTROL METHOD AND APPARATUS Filed Jan. 17, 1941 4 Sheets-Sheet l INVENTOR-S John J 5/2 [we]; Haly R. Vanflcn: er Q9 3 BY ATTORNEYS.

April 1944- .1. J. SHIVELY ETAL 2,347,514

CONTROL METHOD AND APPARATUS Filed Jan. 17, 1941 4 Sheets-Sheet 2 lNVEN 0R5: John J finely far/y R. Mm Derentcr ATTORNEYS.

April 25, 1944.

J.- J. SHIVELY ETAL 23423514 CONTROL METHOD AND APPARATUS Filed Jan. 17, 1941 4 Sheets-Sheet 5 INVENTORSI Ja/m .jlyziveijv ATTORNEYS.

April J. J. SHIVELY EIAL CONTROL METHOD AND APPARATUS Filed Jan. 1'7, 1941 4 Sheets-Sheet 4 INVENTORS= John J S/uve ATTORNEYS.

Patented Apr. 25, 1944 UNITED STATES 2,347,514 CONTROL METHOD AND APPARATUS John J. Shively and Harry R. Van Devcnter, New York, N. Y., assignors, by mesne assignments, to Telephone Answering and Recording Corporation, New York, N. Y., a corporation of Delaware Application January 11, 1941, Serial No. 374,808

15 Claims.

The present invention pertains to improvements in Control methods and apparatus, being a continuation in part of application Serial Number 333,268 filed May 4, 1940, now Patent No. 2,261,420, dated November 4, 1941.

In the above patent application is shown and described a telephone answering and recording device having a starting circuit operable in response to vibratory interruptions of a normally closed detector circuit.

- An object of the present invention is to provide methods and apparatus for the above and iary current input controlled by the thermostat itself.

Further objects and advantages of the invention will become evident during the course oithe following description, in connection with the accompanying drawings, in which- Figure 1 is a diagrammatic view of a preferred form of the invention;

Figure 2 illustrates the enclosure of the thermostatic apparatus;

'Figure 3 is a similar view showing an alternative arrangement of heater elements;

Figure 4 is a similar view showing a second alternative arrangement; and

Figure 5 shows another alternative arrangement.

Referring to Figure 1, the numeral l0 denotes a bimetallic strip held at one end in a stationary metalhc support It. The free end of the strip It) carries front and back contact points l2 and I3 respectively adapted to engage stationary contact screws 14 and E5, the latter being adjustably held in fixed supports it and IT.

A heating coil or element i8 is adapted when energized to heat the bimetallic strip it and cause the latter to bend toward the right. While the oil (8 is shown diagrammatically as ,wound around the strip H) and electrically insulated therefrom, it is obvious that if desired the heating element may be separately mounted closely adjacent the strip Ill, the essential requirement being simply that the coil be so located that its hteat may be readily conveyed to the bimetallic s r p..

The adjustable back contact screw 15 is obnnected through a resistor IS with one lead of' the coil IS. The opposite lead 2! of coil I8 is connected to one conductor 22 of a suitable source of current. The metallic support H of the bimetallic strip I0 is connected via a wire 23 to the second supply conductor 24.

In the general starting or control circuit illustrated, which is typical of the type suitable for 5 use with cyclic devices such as the telephone message recorder set forth in the above-noted copending application Serial Number 333,268, the numeral 25 generally indicate a relay having a magnet 26, normally closed contact 21 and nor- 10 mally open contacts 28 and 29 cooperative with movable arms 30 and 3!, the latter being connected to the supply conductor 25.

It will, of course, be evident that the relay 25 may have any desired number of contacts for l5 controlling additional apparatus, onlysuch parts being shown herein as are pertinent to the illustration of the present invention.

A motor 32, adapted to drive cyclic control cams 33 and 34 through any suitable speed re- 20 ducing means 32 is connected on one side via a lead 35 to the supply conductor 22. The other side of motor 32 is connected via a wire 36 to the normally open relay contact 29.

A breaker 3! normally held closed by the cam 25 '33, is connected by wires 38 and 89 between the relay magnet 26 and the supply lead 22. The other side of the magnet 2E is connected via a lead 4!! to the front contact screw mounting N. The lead 435 is also electrically joined to the normally open relay contact 28.

A detector relay =2! has a movable switch arm d2 adapted to be held clear of a contact point 33 when relay 4| is energized. The relay H is connected on one side via lead to the low voltage secondary winding 65 of a transformer it. A closed circuit through the secondary and the relay 4! is normally maintained through a vibratory breaker, illustrated herein as having a stationary contact member 4-8 and a weighted movable contact member 69. The weighted member 49 normally rests lightly against the stationary member d3, thus maintaining the circuit through relay 4! as noted, but when mechanical vibration, as for example from a telephone bellbox 50, is transmitted through member 48, the weighted member 8 is kicked away from member 48, thus interrupting the circuit.

The primary winding of the transformer 46 is connected on one side to the supply conductor 22 and on the other side via a wire 52, the support H and the lead 23 to the conductor 24.

The contact point 43 of relay it is connected via a lead 53 to the lead 20 of the heating coil E8, while the arm 42 has a connection through wire 42"- with the normally closed relay con tact 21.

A sccond'breaker 54 is cooperative with the cam 34, the lower arm 55 thereof normally resting in an elongated notch 56 in the cam periphery so as to hold the breaker open. Leads 5'? and 5% connect the breaker 5 between the conductor 35 and the wire 52.

In operation, the back contact screw l 5 is normally set to engage the back contact i3 when the temperature of the bimetallic strip 59 is slightly above the highest ambient temperature which can be encountered by the apparatus. Under these circumstances when contact is made, current flows from the supply conductor 25 through the wire 23, support ill, bimetallic strip lb, contact point 53, screw 55 and resistor i9 to the lead 253, thence through the heater coil 33 and lead 25 to the supply conductor 22. The passage of cur-- rent through the coil l3 causes the latter to heat the bimetallic strin, which bends slightly to the right and moves the contact point l3 out of contact with the screw it, breaking the above de-' scribed circuit.

The circuit remains open until the bimetallic strip lfi cools slightly and bends to the left to restore the contact, again causing heating as described, whereupon the above action is repeated.

Due to the presence of the resistor 39, the sta bilizing current supplied to the coil i8 as above described is of comparatively low value, being in the nature of a trickle current, so that the heating described is gradual with very little heat lag between the coil is and strip lb. The gaps successively produced between the point i3 and screw i 5 are therefore very small, the total movement of the point i3 being only suificient to barely make and break the trickle circuit.

In practice the resistance of resistpr i9 is made such that the current now is just sumcient to keep the strip ill heated to the above described breaking point when the ambient temperature is at the lowest value to be encountered. If ole.- sired in some cases a suitable condenser may be connected across the contact members i3 and 55 to reduce any sparking which may occur between them.

t will be seen from the above description that the efiect of the stabilizing current is to normally hold the bimetallic strip ii at a substantially constant temperature and initial position irrespective of ambient temperature changes.

When the coil l8 receives main operating current, the operation is as follows, the input impulses being illustrated herein as initiated by vibraticn of the telephone bell-box spring 59 snaps the arm d2 into contact with contact point 33. A circuit is thereby completed from supply conductor 2 through the main relay arm 36, contact 27, lead 2 arm 52, contact 53, wire 53, lead '20, heater coil ill and lead 28 to the supply conductor 22, thus throwing full supply line voltage across the heater coil. The heating efiect thereby produced bends the bimetallic strip 38 to the right away from the back contact. Successive impulses of current, for example due to successive vibrations of the telephone bellboxcll as described, produce cumulative heating ply conductor 23 through the arm 3i, contact 29 and wire 38 to the motor 32, thence through lead 35 to the conductor 22, thus starting the motor 32 which drives the cams 33 and 35. At the same time the opening of the relay contact 2i breaks the previously described full line current supply circuit through the heater element is, this circuit thereafter remaining open irrespective of any action of the relay 4H so long as the relay magnet 25 remains energized. Furthermore, due to the closure of relay contact 28, a holding circuit is set up through the magnet 25, lead 39, breaker 37 and lead 38 which holds the magnet 28 energized so long as the breaker 3i remains closed. 4

The motor 32, having been started as described, revolves the cams 33 and 35 as indicated by the arrows.

As the notch in cam 31% moves through a few initial degrees of its rotation the breaker arm 55 is forced upward, closing the breaker 5 5. Thereby a second connection between supply conductors 22 and 24 through the motor 32 is established via leads 35 and 5?, breaker 55, leads 58 and 52, support 1; and wire 23. It will be evident that the last-named connection through the motor 32 persists until the cam 34 completes its revolution and the notch 56 permits the breaker 5:3 to re-open as shown. Just prior to the opening of breaker 55, a notch 33 111 cam 33 permits a momentary opening of the breaker 31, thus deenergizing the holding circuit of relay magnet 25 and allowing the relay 25 to return to normal condition as shown.

During the cyclic rotation of the cams 33 and 3 3, the heater coil is is free of main operating current as previously noted, allowing the bimetallic element It? to cool and bend to the left until the point !3 again engages the contact screw is, Thercupon the trickle current operation is re-established to hold the member it substantially at constant temperature and position ready for the next input of main operating current to the heater id.

The main heating current supplied to the coil it, being much heavier than the stabilizing or trickle current, causes comparatively high heating and rapid bending of the bimetallic element iii, so that the gap between the point 52 and screw M for time delay operation is normally made comparatively large. In comparison to this gap the amplitude of movement between the back contact point I3 and screw H5 in making and breaking the trickle current is so small as to be practically negligible. The amount of additional rapid heating efiect necessary to establish contact between point l2 and screw Iii for any normal adjustment of the screw is therefore remains substantially constant irrespective of ambient temperature changes within the range of the apparatus.

In a typical case of operating current impulses occurring in regular succession due to ringing vibrations of a telephone box 50, it is evident that the duration of time necessary for a ring or regular succession 'of rings to cause contact between point l2 and screw IA may be set as desired by adjustment of the screw 14. Similarly, it it is desired to operate a starting circuit by any other means of main current input control to the coil [8, as for example by a manual key or switch 6|, the time interval from closure of key 6| to the actuation of relay 25 is determined by the setting of screw 14 and is substantially independent of ambient temperature since the element In is held at substantially constant initial temperature and position by the trickle current as described.

In Figure 3 the circuits and apparatus illustrated and the operation thereof are substantially the same as those of Figure 1, except that the trickle current, instead of being directed through the main heater coil I8, is directed through an auxiliary heating coil 62 .on or closely adjacent the bimetallic member l0, and in this case the auxiliary heating coil 62 also serves the purpose of the'resistor 19, Figure 1, in limiting the magnitude of the trickle current.

In Figure 4, the arrangement and operation are the same as those of Figure 1 except that the bimetallic element [6 has sufficient resistance that the trickle current passing therethrough.

causes the necessary stabilizing heat to be produced in the element itself. In this case the back contact screw is connected to the line conductor 22 through the resistor l9, though if the resistance of element H1 is sufficiently high the exterior resistor 19 may be omitted. In this embodiment the magnet 26 of the relay 25 is wound to operate on the reduced current due to the resistance of the bimetallic element "i in series, and a suitable resistor 63 is inserted in series with the contact 28 to similarly restrict the holding current.

In the embodiment shown in Figure 5, both the stabilizing or trickle heat and the main operating current are produced in the bimetallic element It without the use of any other heating element. The contact point 43 of detector relay 4! is connected through a lead 64 and a suitable flexible connector 65 with the free or movable end of the element I0 The arm 42 of relay H is connectedas before via its lead 42 to normally closed contact point 21 of main relay 25 but the point 21 instead of engaging arm 30, is provided with an independent arm 66 connected via a branch 61 with the supply conductor 22. The back contact screw is connected through the resistor is with the supply conductor 22.

Normally the trickle current flows from conductor 22 through the resistor t9, the contact screw I5, the back contact point [3, the'thermostatic member l and the lead 23 to the supply conductor 24. Stabilizing heat is thereby produced in the element 10 as previously described. Closure of either relay H or manual switch 5! directs current from the conductor 22 viathe lead 61., arm 66, contact pointzl lead 42 and flexible connector 65 to the element lo By this -i means the resistor is and back contact screw l5 and point 13 are by-passed, full supply voltage being applied through the element In with consequent increased heating until the relay 25* is energized as before,

The comparatively heavy operating current used in heating the thermostatic element produces heat therein so rapidly that any differences in heat loss during the operating period under varying exterior temperature conditions are normally too small to practically affect the time delay action. However, in special cases where such slight variations could become an appreciable factor, the device may be shielded in any suitable manner to reduce them. For example, a vacuum or gas-filled envelope 68 may be applied as illustrated diagrammatically in Figure 2.

In Figure 2, the bimetallic element It and heater 18 are housed in the evacuated envelope S8. The points I3 and I4 areadapted to engage back and main or front contacts 69 and 10. To avoid adjustments within the sealed envelope, the points 69 and I0 are supported in fixed position, and adjustment of the main operating time is provided by inserting an exterior variable resistor H in series with the heater coil I8. I! adjustment of the trickle current is desired, its exterior resistor l9 may also be made variable. as shown. It will be understood that a suitable envelope may similarly be used with the forms of apparatus shown diagrammatically in Figures 1, 3, 4, and 5.

The thermostatic elements have been shown as substantially straight bimetallic strips, but

it will be understood that these diagrammatic showings are illustrative, it being obvious that the thermostatic elements may he of any suitable shapes and types,

From the foregoing description it will be evident that the inventionpr'ovides a method in which a thermostatic device of the character described is self-compensating or stabilizing against variation in normal operation under various exterior temperature conditions within its range. the stabilization or compensation being controlled by the main thermostatic element itself without the necessity for any auxiliary thermostatic members.

While the invention; has been set forth in preferred manner, it is not limited to the exact forms and .circuits illustrated, as various-modifications in apparatus and method may be made without departing from the scope of the appended claims.

What is claimed is:

l. The method of operating a thermostatic device which includes first pro-heating the device to a desired temperature by means controlled by said device, secondly maintaining said device at said pro-heated temperature by the intermittent application of heat thereto under the control of said device, and thirdly, raising the temperature of said pre-heated device above said first temperature by the application of additional heat thereto.

, 2. The method of operating a thermostatic de vice which includes the step of pre-heating the device to a desired temperature by heating means controlled by said device, the second step of maintaining said temperature by said means durin normal non-operating periods of the device, and the third step of raising the temperature of said pre-heated device above said first temperature by applying extra heat thereto to cause said device to operate.

3. The method of operating a thermostatic device tocontrol a circuit which includes the steps of first pro-heating the device to a desired temperature, secondly normally maintaining said temperature under control of said device and, thirdly, raising the temperature ofsaid device above said first temperature to actuate said device to control a circuit.

4. That method of stabilizing a control device by heat to control a circuit, means controllable by said thermostatic member to normally maintain said member substantially at a pre-determined temperature higher than the temperature of the surrounding media, and means to heat said member above said pre-determined temperature said member and thereby control said circuit.

8. In a device of the character described, a thermostatic member, electric heating means adapted to supply'heat to said member, means to direct operating current through said heating means to actuate said member, and means controllable by said member to normally direct a trickle current through said heating means whereby said member may normally be maintained substantially at a pre-determined temperature.

7. In a thermal delay device, in combination,

a main contact member, an auxiliary contact member, a heat responsive member normally engaging said auxiliary contact member and normally spaced from said main contact member, an electric heater associated with said heat responsive member and adapted to furnish heat thereto, a resistor connected in series between said auxiliary contact member and said heater, a source of current, means to normally form a stabilizing circuit from said source through said heat responsive member, said auxiliary contact member, said resistor and said heater, and means to direct actuating current through said heater independently of said auxiliary contact member and said resistor to move said heat responsive member into engagement with said main contact member.

8. The invention claimed in claim 7 including a casing enveloping said heat responsive memher, said contact members and said heater.

9. In a device of the character described, in combination, a bimetallic switch member, a main contact member normally spaced from said bimetallic member, an auxiliary contact member adapted to be normally engaged by said bimetallic member,'said bimetallic member being operable by cumulative heat to engage said main contact member, means controllable by said himetallic member and said auxiliary contact member to maintain said bimetallic member normally heated to a ore-determined temperature, and means to furnish cumulative operating heat to said bimetallic member above said pie-determined temperature.

10. In a device of the character described, in combination, a bimetallic member, electric heating means in heat exchange relationship with said bimetallic member, switching means cooperative with said bimetallic member when said member is heated to a pre-determined degree, second switching means normally cooperative with said bimetallic member, a resistor in electrical series between said second switching means and that of the surrounding medium to operate and said heater, and means to direct current through said heater independently of said second switching means and said resistor.

11. In a device of the character described, in combination, switching means thermally operable by electric current to control an electric circuit at a pre-determined temperature, means to supply operating current to said switching means, an aumliary contact member normally cooperative with said switching means, andmeans controllable through said switching means and said auxiliary contact member to supply auxiliary heating current to said switching means whereby said switching means is normally maintained substantially at a second pro-determined temperature below said operating temperature.

12. The invention claimed in claim 11 includingan air-tight casing enveloping said switching means and auxiliary contact member, and a variable resistor in said operating current supply means, said resistor being exterior to said casing and adjustable to vary said operating current.

combination, a bimetallic member adapted to be heated by electric current passing therethrough, a main contact member normally spaced from said bimetallic member, an auxiliary contact member normally engageable by said bimetallic 14. In a device of the character described, a

thermally operable relay having a movable contact member normally biased in one direction, first and second contact members each adapted when contacted by said movable member to complete a circuit independent of the other, said movable member in its normally biased position being in electrical contact with said first contact member, heating means adjacent said movable member and adapted to heat and thereby cause said member to move out of its normally biased position and open said electrical contact with b said first fixed member and assume a position between said first and second fixed members and out or contact with both of them, means for applying electric current to said heating means to maintain same at a. temperaturesuificient to cause said movable member to move alternately into and out of contact'with said first contact member and without making contact with said second contact member, and means for causing an additional current to flow through said heat ing means and thereby cause said movable member to contact said second contact member.

15. The combination as claimed in claim 14 wherein the thermally operable relay comprising the fixed and movable contact members together with the heating means are enclosed in an air-tight envelope and provided with'circuit connections extending through a wall thereof.

JOHN J. SHIVELY. HARRY R. VAN DEVENTER.

13. In a device of the character described, in 

